The invention relates to a bulb socket that feeds power to a wedge base bulb by holding the wedge base bulb, more particularly, to an improved bulb socket that can effectively keep the bulb from being detached therefrom.
A wedge base bulb and a bulb socket to which the wedge base bulb is attached are used, e.g., in a lamp of an automobile. Generally, the bulb socket has a socket main body, and inside the socket main body is a bulb holding chamber that is opened upward to allow the bulb to be accommodated therein. A pair of bulb clamping pieces having resiliency are attached to the inside of the bulb holding chamber so that the base portion of the bulb inserted into the bulb holding chamber can be clamped with resiliency and come in contact with leads extending on the base to electrically connect the bulb socket to the bulb.
For, example, a bulb socket for feeding power by holding a wedge base bulb such as shown in FIG. 1 has heretofore been known. That is, a bulb insertion hole 104 that allows a base portion 103a of a wedge base bulb 103 to be inserted thereinto and a connector insertion hole 105 that allows a connector (not shown) to be inserted thereinto are arranged on the upper side and on the lower side of the main body 102 of a bulb socket 101. Holding metals 106, each holding the base portion 103a of the wedge base bulb 103 and supplying power thereto, are attached to both sides of the bulb insertion hole 104 on the upper side. Each holding metal 106 has a terminal 106a at a lower portion thereof and holding pieces 106b formed by bending the bifurcated portions of the terminal 106a inward in the middle. A pair of holding portions 106c are formed by further bending the upper portions of the holding pieces 106b inward to be given resiliency for clamping the base portion 103a.
To attach the wedge base bulb 103 to the thus constructed socket main body 102, the base portion 103a is inserted into the bulb insertion hole 104 and then set between the holding portions 106c. As a result, the holding portions 106c come to clamp the base portion 103a by way of single-point support at both left and right sides to allow the wedge base bulb 103 to be attached to the socket main body 102.
However, such conventional structure addresses the problem that the holding strength is weak, because the base portion 103a of the wedge base bulb 103 is attached to the socket main body 102 while held by way of single-point support, i.e., only by the holding portions 106c of the holding metal 106. As a result, when a strong impact is applied to the wedge base bulb 103, the wedge base bulb 103 is likely to be detached from the socket main body 102 if the wedge base bulb is disposed at a position close to the trunk compartment of an automobile such as at the high mount stop lamp or the license plate lamp, because the impact applied to these lamps is strong and the strength of the socket main body 102 to hold the wedge base bulb 103 is not sufficient.
In addition, although it is conceivable to improve the holding strength by increasing resiliency while using thicker special members at the holding portions, such design is disadvantageous in terms of parts cost.
A conventionally taken measure to this problem is disclosed in Japanese Unexamined Utility Model Publication No. 2-47782. The main portion of the structure disclosed in the above publication is shown in FIG. 2. That is, projected portions c bulge out on both upper surfaces of a base portion b of a bulb a, and resilient retaining pieces f retained by the projected portions c are formed on the inner surface of a bulb holding chamber e of a socket main body d.
However, this structure is characterized as arranging the detached prevention portion (the projected portions c and the resilient retaining pieces f) as well as electrical connection portion (the bulb clamping pieces) separately from each other. Therefore, the internal structure of the socket main body d is complicated, which in turn complicates the mold, thus elevating the cost of manufacture. In addition, a specially specified bulb a with the projected portions c provided must be prepared, which does not meet a requirement of general-purpose structure.